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Title: The rhg1‐a ( Rhg1 low‐copy) nematode resistance source harbors a copia‐family retrotransposon within the Rhg1‐ encoded α‐SNAP gene

Soybean growers widely use theResistance toHeteroderaglycines1 (Rhg1) locus to reduce yield losses caused by soybean cyst nematode (SCN).Rhg1is a tandemly repeated four gene block. Two classes of SCN resistance‐conferringRhg1haplotypes are recognized:rhg1‐a(“Peking‐type,” low‐copy number, three or fewerRhg1repeats) andrhg1‐b(“PI 88788‐type,” high‐copy number, four or moreRhg1repeats). Therhg1‐aandrhg1‐bhaplotypes encode α‐SNAP (alpha‐SolubleNSFAttachmentProtein) variants α‐SNAPRhg1LC and α‐SNAPRhg1HC, respectively, with differing atypical C‐terminal domains, that contribute to SCN resistance. Here we report thatrhg1‐asoybean accessions harbor a copia retrotransposon within theirRhg1 Glyma.18G022500(α‐SNAP‐encoding) gene. We termed this retrotransposon “RAC,” forRhg1alpha‐SNAPcopia. Soybean carries multipleRAC‐like retrotransposon sequences. TheRhg1 RACinsertion is in theGlyma.18G022500genes of all truerhg1‐ahaplotypes we tested and was not detected in any examinedrhg1‐borRhg1WT(single‐copy) soybeans.RACis an intact element residing within intron 1, anti‐sense to therhg1‐a α‐SNAPopen reading frame.RAChas intrinsic promoter activities, but overt impacts ofRACon transgenic α‐SNAPRhg1LC mRNA and protein abundance were not detected. From the nativerhg1‐a RAC+genomic context, elevated α‐SNAPRhg1LC protein abundance was observed in syncytium cells, as was previously observed for α‐SNAPRhg1HC (whoserhg1‐bdoes not carryRAC). Using a SoySNP50K SNP corresponding withRACpresence, just ~42% of USDA accessions bearing previously identifiedrhg1‐aSoySNP50K SNP signatures harbor theRACinsertion. Subsequent analysis of several of these putativerhg1‐aaccessions lackingRACrevealed that none encodedα‐SNAPRhg1LC, and thus, they are notrhg1‐a.rhg1‐ahaplotypes are of rising interest, withRhg4, for combating SCN populations that exhibit increased virulence against the widely usedrhg1‐bresistance. The present study reveals another unexpected structural feature of manyRhg1loci, and a selectable feature that is predictive ofrhg1‐ahaplotypes.

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Author(s) / Creator(s):
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Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Plant Direct
Medium: X
Sponsoring Org:
National Science Foundation
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